1. Field of the Invention
The present invention is generally directed at an improved method for detecting minute cracks in the surface of an article and automatically and/or manually repairing detected cracks, and specifically at detecting cracks in the surface of turbine engine hardware and automatically and/or manually repairing detecting such cracks with the aid of fluorescent penetrant.
2. Discussion of the Prior Art
In the course of engine operation, turbine engine hardware typically experiences minor damage as a result of engine operation. This damage can take many forms such as minor pits and cracks and may be as a result of any one of a number of conditions, such as ingestion of foreign particles, wear, erosion or fatigue. Frequently, the damage is of a minor nature, and after a repair operation, the hardware is suitable for reuse.
Currently, the articles to be repaired are visually inspected under suitable white light after cleaning so that defects or indications can be visually detected. In order to identify very fine cracks, visual inspection under magnification is conducted. As the cracks are identified by the operator, a suitable alloy in the form of a slurry is applied by the operator. The crack identification procedure and alloy application is the first step in well known repair procedures such as activated diffusion healing (ADH), partitioned alloy component healing (PACH) and brazing. After the application of the alloy, the articles are heated at elevated temperatures according to the selected procedure, ADH, PACH or brazing, which causes the alloy to flow and "heal" the defect.
After the repair procedure, the article is fluorescent penetrant inspected according to well-known procedures. These procedures require cleaning of the part, inspection of the part under an ultraviolet light, identification of any remaining defects, cleaning of the part and reapplication of the slurry for re-repair of any additionally identified defects. Of course, the problem with the procedure is that the subsequent fluorescent penetrant inspection frequently identifies defects that are not resolved or resolvable using the visual inspection techniques, with or without the aid of magnification. A process that can properly identify the defects present in the article prior to the repair cycle without adversely affecting the repair can save time, manpower, effort and energy resources if the entire repair can be completed in one cycle.